Proximity limit switch

ABSTRACT

This specification describes a proximity electrical limit switch which is operated by a change in magnetic field strength caused by passing a metal cam or other object in the proximity of magnetically controlled electrical contacts. The switching action is made reliably responsive to even inaccurately guided cams by the use of a U-shaped switch body construction including special wing-shaped guiding structures and a flexible switch body mounting.

United States Patent [72] Inventor Max Bauer [56] References Cited Offenhausen, Germ ny UNITED STATES PATENTS PP'- 380,670 2 843 697 7 1958 B ck 33 7 221 Filed Nov. 28, 1969 e 5/20 [45] Patented June 15, 1971 Pru nary Examiner-G. Harris [73] Assignee Hans Lingl Maschinenfabrik GmbH Ema", JR

Germany ArrorneyCushman. Darby & Cushman {32] Priority Nov. 30, 1968 [33] Germany [31] P18 11 904.5

ABSTRACT: This specification describes a proximity electri- [54] M FS cal limit switch which is operated by a change in magnetic alms ramng field strength caused by passing a metal cam or other object in [52] US. Cl 335/205 the proximity of magnetically controlled electrical contacts. [51 Int. Cl HOlh 3/16, The switching action is made reliably responsive to even inac- HOlh 36/00 curately guided cams by the use of a U-shaped switch body [50] Field of Search 335/153, construction including special wing-shaped guiding structures and a flexible switch body mounting.

PATENTED JUN 1 5 ran MAX I ATTORNEYS PROXIMITY LIMIT SWITCH This invention generally relates to electrical switching devices and more specifically to magnetically operated limit or proximity switches which are designed to switch electrical contacts, such as those in a magnetic reed switch, whenever an associated magnetic field is altered by the influence of a magnetically permeable or nonpermeable member which is properly positioned in the proximity of the switch structure.

Although there have been prior art switches of this general type, they have all exhibited seriousdeficiencies for use in environments where mechanical tolerances cannot be closely controlled. The quiescent magnetic field strength of such prior art devices is usually held at a relatively low value to effect required sensitivity or switching precision. Because of this plus prior art switch body configurations, a cam or magnetically permeable member must be precisely guided with respect to all these devices to effect a desired switching operation.

Accordingly, it is an object of this invention to devise a magnetically operated proximity switch that may be reliably operated with cams that can only be inaccurately guided such as for example in association with transport tracks and other rough operations in the brick, structural clay and mining industries.

A more complete and detailed understanding of this invention may beobtained by referring to the following description and the drawings of which:

the FIGURE is a three-dimensional view of one embodiment of this invention. I

Briefly, the disclosed embodiment of this invention comprises a U-shaped switch body where one leg of the U is a magnet or other source of magnetic field flux and the remaining leg is an electrical switch contact assembly such as a magnetic reed switch subject to mechanical influence caused by a magnetic field. A cam or other magnetically permeable member is guided by a structural guide means through the space between the two legs of the Ushaped body and by concentrating magnetic flux within the cam, the magnetic field near the switch contacts is momentarily reduced or interrupted thus causing exceptionally reliable operations of the electrical switch contacts. Of course, if desired, a magnetically nonpermeable cam might be used instead to interrupt the magnetic field near the switch contacts. lnaccurate movements of the cam are compensated for by structural guide means in combination with an elastic or flexible mounting means for the U-shaped body which mounting allows the body to swing with an inaccurately aligned cam in response to mechanical pressure on either the switch body or the structural guide means.

Referring to the FIGURE, a specificembodiment is shown where a U-shaped switch body includes permanent magnet 3 on one side and switch contacts 4 on the opposite side. A cam 1, moving in the general direction of the arrows shown in the FIGURE, is guided between these two sides by, guide means 2 generally shown as wing-shaped structures with guiding faces outwardly inclined from inside faces of the U=shaped switch body. An elastic mounting means 5 mechanically connects the switch body to a solid base while yet allowing the switch body to swing or flex with inaccurately aligned cams. Two flexible elastic structures are shown in the FIGURE. The mounting means is comprised by an assembly of these two structures which are aligned parallel tothegeneral direction of cam movements thus permitting the switch structure to move more easily in a direction transverse to general cam movements than in a parallel direction. Or, in other words, the composite flexible mounting means 2 provides less resistance to transverse movements than to parallel movements of the switch body with respect to the general direction of cam movements.

While only one embodiment of this invention has been described in this application, it will be readily apparent that one skilled in the art could make several obvious modifications without departing from the scope of this invention.

Whatlclaim is: h 1. An electrical proximity limit switch for mounting on a support structure having a switch body with at least two sides and of the type that is operated by nearby movements of a magnetically permeable cam, said switch comprising:

a source of magnetic flux included in one of said sides,

magnetically operated switch contacts included in the other of said sides,

said'two sides spaced apart to of said cam, and

flexible mounting means attached both to said switch body and to said support structure for allowing said switch body to move with respect to said support structure in compensation for inaccurate cam movements.

2. An electrical proximity limit switch adapted for mounting on a supporting structure and for operation by a cam moving in one general direction, said switch comprising:

a U-shaped structure having a first side and a second side,

a flexible mounting member connected to said U-shaped structure,

a source of magnetic flux included in said first side, and

a magnetically operated electrical switch contact included in said second side.

3. Anelectrical proximity limit switch as in claim 2 including guide means for guiding said cam through an opening between said first and second sides.

4. An electrical proximity limit switch as in claim 3 wherein said guide means comprises wing-shaped structures with outwardly bent faces attached to said sides.

5. An electrical proximity limit switch as in claim 2 wherein said flexible mounting member includes:

a first effective dimension aligned substantially parallel to said one general direction of cam movement between said sides,

a second effective dimension aligned substantially transverse to said one general direction of cam movement between said sides, and where said first dimension is greater than said second dimension thus causing less resistance to movements in said transverse direction than in said parallel direction.

6. An electrical proximity limit switch as in claim 2 wherein said flexible mounting member permits said switch body to flex in a direction generally transverse to said one general direction of cam movements between said sides but is substantially inflexible in other directions.

allow passage therebetween 

1. An electrical proximity limit switch for mounting on a support structure having a switch body with at least two sides and of the type that is operated by nearby movements of a magnetically permeable cam, said switch comprising: a source of magnetic flux included in one of said sides, magnetically operated switch contacts included in the other of said sides, said two sides spaced apart to allow passage therebetween of said cam, and flexible mounting means attached both to said switch body and to said support structure for allowing said switch body to move with respect to said support structure in compensation for inaccurate cam movements.
 2. An electrical proximity limit switch adapted for mounting on a supporting structure and for operation by a cam moving in one general direction, said switch comprising: a U-shaped structure having a first side and a second side, a flexible mounting member connected to said U-shaped structure, a source of magnetic flux included in said first side, and a magnetically operated electrical switch contact included in said second side.
 3. An electrical proximity limit switch as in claim 2 including guide means for guiding said cam through an opening between said first and second sides.
 4. An electrical proximity limit switch as in claim 3 wherein said guide means comprises wing-shaped structures with outwardly bent faces attached to said sides.
 5. An electrical proximity limit switch as in claim 2 wherein said flexible mounting member includes: a first effective dimension aligned substantially parallel to said one general direction of cam movement between said sides, a second effective dimension aligned substantially transverse to said one general direction of cam movement between said sides, and where said first dimension is greater than said second dimension thus causing less resistance to movements in said transverse direction than in said parallel direction.
 6. An electrical proximity limit switch as in claim 2 wherein said flexible mounting member permits said switch body to flex in a direction generally transverse to said one general direction of cam movements between said sides but is substantially inflexible in other directions. 